Intermolecular Forces and Solutions Flashcards
Definition of intermolecular forces
force of attraction that occurs between atoms, molecules, and ions due to their proximity in space to each other
What’s stronger - intermolecular or intramolecular forces?
INTRAmolecular are stronger
What affects the strength of attraction?
- Magnitude of charge (real or partial)
- distance between species
The stronger the attractive forces between the particles , the more they -
resist moving or breaking apart
What is polarity?
The separation of electrical charge along a bond due to differences in the electronegativity of the bonded atoms
What leads to the formation of partial charges? (negative or positive)
Electron density not being equally shared between the two atoms
What is surface tension?
A liquid’s resistance to increase its surface area
- the stronger the intermolecular forces, the more energy required to increase the surface area
How does a liquid minimize surface area?
it forms spherical drops
What is capillary action?
the spontaneous rising of a liquid in a narrow tube or the movement of a liquid up a piece of paper against the pull of gravity
- the result of cohesive and adhesive forces
What is viscosity?
The measure of a liquid’s resistance to flow
- the amount of energy necessary to move an object through a fluid
- molecule size plays an important role
What are some applications of intermolecular forces?
- Surface tension
- Capillary action
- Viscosity
- Receptor-Drug binding
- Phase changes
- Solubility
What properties are determined by receptor-drug binding?
Efficacy, potency, and toxicity
What does phase changes represent?
Changes in the phase of a substance with respect to temperature and pressure
- energy is required to disrupt molecular interactions and thus leads to changes in the states of matter
What does solubility depend on?
Attractive forces of the solute and solvent
- substances with similar polarity will be soluble or miscible
- “like dissolves like”
What is the weakest intermolecular force?
Van der Waals forces
What is a Van der Waals force?
Interaction arising from the formation of induced dipoles between two non-polar molecules (or portions of molecules)
What are dipole-dipole interactions?
- occurs in all polar molecules
- relatively strong interaction, but depends on the nature of the individual dipoles involved
Hydrogen bonding
Very strong specialized dipole-dipole interaction
- H bond donor and H bond acceptor
Ion-dipole
Very strong interaction between a full formal charge and a dipole
- depends somewhat on the strength of the dipole
Electrostatic interactions
- ionic interactions between a cationic portion and anionic portion
- effective at distances farther than other types of interactions
- persist longer than other interactions
Which intermolecular force is the strongest?
Covalent bonds
What is a solution?
homogenous mixture of two or more substances
What is a solvent?
Major component of the mixture (usually water)
What is a solute?
the minority component of the mixture
What does an aqueous solution mean?
the solvent is water
What determines the solubility of one substance in another?
- intermolecular forces (like dissolves like)
- tendency to mix
What does it mean if a compound is more water soluble?
it has more polar bonds
What does a saturated solution mean?
a solvent is holding the maximum amount of solute dissolved
- even if you add more, it won’t dissolve
What does an unsaturated solution mean?
a solution where the solvent holds less than the maximum amount of solute dissolved
- more solute will dissolve if added
What does it mean if a solution is supersaturated?
The solvent holds more than the maximum amount of solute dissolved
- usually unstable
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How to calculate molecular weight -
add the sum of each atoms and how many there are
How to calculate moles -
Mass of sample(g) /molecular weight (g/mol)
How to calculate density -
Mass of sample (g)/ Volume of sample (mL)
How to calculate Molarity (M)
moles of solute (mol) / L of solution
Weight percent
a percentage of the solute mass in the mass of the solution
- assume a 100g sample
- percent becomes mass (g) / 100g
Volume percent
solution concentration expressed as a percentage of the solute volume in the volume of the solution
- assume a 100 ml sample
- percent becomes volume (ml) / 100 mL
